by Tim Harding
The informal fallacy known as argumentum ad populum means ’argument from popularity’ or ‘appeal to the people’. This fallacy is essentially the same as ad numerum, appeal to the gallery, appeal to the masses, common practice, past practice, traditional knowledge, peer pressure, conventional wisdom, the bandwagon fallacy; and lastly truth by consensus, of which I shall say more later.
The Argument from Popularity fallacy may be defined as when an advocate asserts that because the great majority of people in general agree with his or her position on an issue, he or she must be right. In other words, if you suggest too strongly that someone’s claim or argument is correct simply because it’s what most people believe, then you’ve committed the fallacy of appeal to the people. Similarly, if you suggest too strongly that someone’s claim or argument is mistaken simply because it’s not what most people believe, then you’ve also committed the fallacy.
Agreement with popular opinion is not necessarily a reliable sign of truth, and deviation from popular opinion is not necessarily a reliable sign of error, but if you assume it is and do so with enthusiasm, then you’re guilty of committing this fallacy. The ‘too strongly’ mentioned above is important in the description of the fallacy because what most everyone believes is, for that reason, often likely to be true, all things considered. However, the fallacy occurs when this degree of support is used as justification for the truth of the belief.
It often happens that a true proposition is believed to be true by most people, but this is not the reason it is true. In other words, correlation does not imply causation, and this confusion is the source of the fallacy, in my view. For example, nearly every sane person believes that the proposition 1+1=2 is true, but that is not why it is true. We can try doing empirical experiments by counting objects, and although this exercise is highly convincing, it is still only inductive reasoning rather than proof. Put simply, the proposition 1+1=2 is true because it has been mathematically proven to be true. But my purpose here is not to convince you that 1+1=2. My real point is that the proportion of people who believe that 1+1=2 is true is irrelevant to the truth or falsity of this proposition.
Let us now consider a belief where its truth is less obvious. Before the work of Copernicus and Galileo in the 15th and 16th centuries, most people (including the Roman Catholic Church) believed that the Sun revolved around the Earth, rather than vice versa as we now know through science. So the popular belief in that case was false.
This fallacy is also common in marketing e.g. “Brand X vacuum cleaners are the country’s most popular brand; so buy Brand X vacuum cleaners”. How often have we heard a salesperson try to argue that because a certain product is very popular this year, we should buy it? Not because it is a good quality product representing value for money, but simply because it is popular? Weren’t those ‘power balance wrist bands’ also popular before they were exposed as a sham by the ACCC?
For another example, a politician might say ‘Nine out of ten of my constituents oppose the bill, therefore it is bad legislation.’ Now, this might be a political reason for voting against the bill, but it is not a valid argument that the bill is bad legislation. To validly argue that bill is bad legislation, the politician should adduce rational arguments against the bill on its merits or lack thereof, rather than merely claim that the bill is politically unpopular.
In philosophy, truth by consensus is the process of taking statements to be true simply because people generally agree upon them. Philosopher Nigel Warburton argues that the truth by consensus process is not a reliable way of discovering truth. That there is general agreement upon something does not make it actually true. There are several reasons for this.
One reason Warburton discusses is that people are prone to wishful thinking. People can believe an assertion and espouse it as truth in the face of overwhelming evidence and facts to the contrary, simply because they wish that things were so. Another is that people are gullible, and easily misled.
Another unreliable method of determining truth is by determining the majority opinion of a popular vote. This is unreliable because on many questions the majority of people are ill-informed. Warburton gives astrology as an example of this. He states that while it may be the case that the majority of the people of the world believe that people’s destinies are wholly determined by astrological mechanisms, given that most of that majority have only sketchy and superficial knowledge of the stars in the first place, their views cannot be held to be a significant factor in determining the truth of astrology. The fact that something ‘is generally agreed or that ‘most people believe’ something should be viewed critically, asking the question why that factor is considered to matter at all in an argument over truth. He states that the simple fact that a majority believes something to be true is unsatisfactory justification for believing it to be true.
In contrast, rational arguments that the claims of astrology are false include firstly, because they are incompatible with science; secondly, because there is no credible causal mechanism by which they could possibly be true; thirdly, because there is no empirical evidence that they are true despite objective testing; and fourthly, because the star signs used by astrologers are all out of kilter with the times of the year and have been so for the last two or three thousand years.
Another example is the claims of so-called ‘alternative medicines’ where judging by their high sales figures relative to prescription medicines, it is quite possible that a majority of the population believe these claims to be true. Without going into details here, we skeptics have good reasons for believing that many of these claims are false.
Warburton makes a distinction between the fallacy of truth by consensus and the process of democracy in decision making. Descriptive statements of the way things are, are either true or false – and verifiable true statements are called facts. Normative statements deal with the way things ought to be, and are neither true nor false. In a political context, statements of the way things ought to be are known as policies. Political policies may be described as good or bad, but not true or false. Democracy is preferable to other political processes not because it results in truth, but because it provides for majority rule, equal participation by multiple special-interest groups, and the avoidance of tyranny.
In summary, the Argument from Popularity fallacy confuses correlation with causality; and thus popularity with truth. Just because most people believe that a statement is true, it does not logically follow that the statement is in fact true. With the exception of the demonstrably false claims of astrology and so-called ‘alternative medicines’, popular statements are often more likely to be true than false (‘great minds think alike’); but they are not necessarily true and can sometimes be false. They are certainly not true merely because they are popular. This fallacy is purely concerned with the logical validity of arguments and the justification for the truth of propositions. The identification of this fallacy is not an argument against democracy or whether popular political policies should or should not be pursued.
Clark J. and Clark T., (2005) Humbug! The skeptic’s field guide to spotting fallacies in thinking Nifty Books, Capalaba.
 Clark and Clark, 2005.
 Feiser and Dowden et al, 2011.
 Warburton, 2000.
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